全文获取类型
收费全文 | 22336篇 |
免费 | 2227篇 |
国内免费 | 839篇 |
专业分类
耳鼻咽喉 | 84篇 |
儿科学 | 495篇 |
妇产科学 | 285篇 |
基础医学 | 4007篇 |
口腔科学 | 335篇 |
临床医学 | 1188篇 |
内科学 | 3696篇 |
皮肤病学 | 444篇 |
神经病学 | 1336篇 |
特种医学 | 546篇 |
外国民族医学 | 2篇 |
外科学 | 2444篇 |
综合类 | 2589篇 |
现状与发展 | 1篇 |
预防医学 | 1236篇 |
眼科学 | 232篇 |
药学 | 3271篇 |
2篇 | |
中国医学 | 788篇 |
肿瘤学 | 2421篇 |
出版年
2024年 | 64篇 |
2023年 | 657篇 |
2022年 | 1491篇 |
2021年 | 1347篇 |
2020年 | 1055篇 |
2019年 | 1209篇 |
2018年 | 1106篇 |
2017年 | 960篇 |
2016年 | 804篇 |
2015年 | 1007篇 |
2014年 | 1371篇 |
2013年 | 1348篇 |
2012年 | 1109篇 |
2011年 | 1290篇 |
2010年 | 1009篇 |
2009年 | 975篇 |
2008年 | 911篇 |
2007年 | 830篇 |
2006年 | 741篇 |
2005年 | 792篇 |
2004年 | 707篇 |
2003年 | 579篇 |
2002年 | 364篇 |
2001年 | 337篇 |
2000年 | 280篇 |
1999年 | 260篇 |
1998年 | 228篇 |
1997年 | 226篇 |
1996年 | 193篇 |
1995年 | 205篇 |
1994年 | 150篇 |
1993年 | 127篇 |
1992年 | 86篇 |
1991年 | 93篇 |
1990年 | 71篇 |
1989年 | 71篇 |
1988年 | 57篇 |
1987年 | 56篇 |
1986年 | 64篇 |
1985年 | 141篇 |
1984年 | 193篇 |
1983年 | 100篇 |
1982年 | 125篇 |
1981年 | 136篇 |
1980年 | 93篇 |
1979年 | 90篇 |
1978年 | 69篇 |
1977年 | 53篇 |
1976年 | 50篇 |
1975年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Correlation between 5-HT7 receptor affinity and protection against sound-induced seizures in DBA/2J mice 总被引:2,自引:0,他引:2
Anne Bourson Véronique Kapps Catherine Zwingelstein Alain Rudler Frank G. Boess A. J. Sleight 《Naunyn-Schmiedeberg's archives of pharmacology》1997,356(6):820-826
Audiogenic seizures can be induced in DBA/2J mice following intense auditory stimulation. A number of neurotransmitters, including
5-hydroxytryptamine (5-HT), are believed to be involved in mediating this effect since it has been shown previously that depletion
of 5-HT or blockade of 5-HT receptors protects DBA/2J mice from these audiogenic seizures. The present study was undertaken
to determine whether antagonism of the newly identified 5-HT7 receptor may protect DBA/2J mice from audiogenic seizures by attempting to correlate in vivo potency of compounds with their
affinity at the 5-HT7 receptor. All compounds used in the correlation were shown to be antagonists at the 5-HT7 receptor and a statistically significant correlation was observed between 5-HT7 affinity and doses for half-maximal response (ED50) for protection of DBA/2J mice from sound-induced seizures (r = 0.80; P < 0.05). No significant correlation was observed between in vivo activity and affinity at either 5-HT1A, 5-HT2A or 5-HT2C receptors. It is also unlikely that interactions between the 5-ht5 receptor will protect DBA/2J mice from audiogenic seizures since metergoline and mesulergine which are both active in this
in vivo model have no affinity for the 5-ht5 receptor. There are similarities between the pharmacology of the 5-HT7 receptor and that of the 5-HT1A receptor, however the correlation between the in vivo potency in DBA/2J mice and 5-HT1A affinity was not significant. Furthermore, the 5-HT1A receptor antagonist WAY 100135 did not protect DBA/2J mice from audiogenic seizures at doses that antagonise 5-HT1A receptor-mediated effects in mice. These data suggest that antagonism of 5-HT7 receptors may protect against audiogenic seizures in DBA/2J mice although a definitive conclusion must await studies with
selective 5-HT7 antagonists.
Received: 20 March 1997 / Accepted: 10 August 1997 相似文献
32.
Pamela H. Orr Victor Dong Marlis L. Schroeder Malcolm R. Ogborn 《Pediatric nephrology (Berlin, Germany)》1995,9(5):612-613
P1 blood group positivity has been postulated as a host factor which may provide protection against the development of post-enteropathic hemolytic uremic syndrome (HUS). In this study, blood group status in 20 Inuit survivors ofEscherichia coli 0157: H7-associated HUS was compared with age-and sex-matched controls from the same community who had experienced uncomplicated diarrheal illness due to the same pathogen. Of 20 HUS survivors, 6 were P1 antigen positive compared with 8 of the 20 controls (P=0.7). We conclude that P1 antigen positivity was not protective against HUS in this population. Further studies of this condition to clarify the role of host factors in verotoxin-induced endothelial damage are indicated. 相似文献
33.
用限制性内切酶EcoRI从pKS(-)HTH_1切下全长为1.9 kb的人酪氨酸羟化酶基因,在T_4DNA连接酶的作用下连接在真核表达载体pCDNA_3的EcoR Ⅰ位点,构建成重组质粒pcD-NA_3HTH_1,该质粒转染COS-7细胞,免疫荧光组织化学染色证实酪氨酸羟化酶在其中的表达。 相似文献
34.
刺梨酸的分离与结构研究 总被引:5,自引:0,他引:5
从刺梨中分离出一种新的五环三萜酸,命名为刺梨酸。通过光谱分析和衍生物的制备,确定其化学结构为2β,3α,7β,19α-四羟基乌苏-12-烯-28-羧酸。 相似文献
35.
超声介导上调Smad7表达对腹膜炎大鼠腹膜炎症和功能的影响 总被引:2,自引:0,他引:2
目的 通过基因转染的方法上调Smad7在大鼠腹膜组织的表达,旨在探讨Smad7的高表达对大鼠腹膜炎模型的炎症反应和腹膜功能的影响。方法 Ⅱ级雄性SD大鼠18只随机分入正常组、对照组和模型组,后两组分别给予空载体和Smad7质粒转染,72 h后腹腔内注射大肠杆菌(E.Coli, ATCC 25922) 109 CFU/kg体重诱导腹膜炎,在48 h后做腹膜功能试验并杀检大鼠。检测腹水及血白细胞计数、腹水细菌菌落计数。间接免疫荧光检测Smad7和CD45在腹膜组织的表达。Western印迹检测腹膜组织Smad7蛋白的表达。应用SPSS 11.0统计软件对腹膜功能与腹水白细胞数和细菌菌落数进行Pearson多元线性相关分析。 结果 与空载体组比较,Smad7转基因组大鼠腹膜组织Smad7的表达、腹水白细胞计数和腹膜组织浸润的白细胞数均显著增加,但腹水细菌菌落计数显著降低、腹膜功能显著恶化。相关分析显示腹膜功能的恶化与腹水白细胞计数相关而与腹水细菌菌落计数无相关。结论 Smad7在大鼠腹膜组织的高表达增强了腹膜局部的炎症反应,而过强的炎症反应导致腹膜功能进一步受损。 相似文献
36.
Monoclonal Antibody Specific for TIRC7 Induces Donor-specific Anergy and Prevents Rejection of Cardiac Allografts in Mice 总被引:1,自引:0,他引:1
Yusuke Kumamoto Antje Tomschegg Fatima Bennai-Sanfourche Anke Boerner Arthur Kaser Isabella Schmidt-Knosalla Thomas Heinemann Mirko Schlawinsky Richard S. Blumberg Hans-Dieter Volk Nalan Utku 《American journal of transplantation》2004,4(4):505-514
T cell immune response c-DNA (TIRC7) is up-regulated during the early stages of T-cell activation in response to alloantigens. In this study, we analyzed the effects of newly developed monoclonal antibodies (mAb) against TIRC7 in acute cardiac allograft rejection. Fully vascularized heterotopic allogeneic heart transplantation was performed in mice across a full-mismatch barrier (C57Bl/10 into CBA). Recipients received seven injections (day 0-7) of a novel anti-TIRC7 mAb or remained untreated. Graft survival, histology and ex vivo lymphocyte functions were tested. Targeting of TIRC7 with an anti-TIRC7 mAb diminishes lymphocyte infiltration into grafts resulting in delay of morphological graft damage and prolongation of allograft survival. The lymphocytes from anti-TIRC7 mAb-treated animals exhibit hypo-responsiveness without evidence of lymphocyte depletion against the donor allo-antigens. Proliferation and expression of interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha) were down-regulated while interleukin-4 (IL-4) and IL-10 expression were spared. Moreover, anti-TIRC7 mAb enhanced up-regulation of CTLA-4 expression but suppressed up-regulation of CD25 on stimulated lymphocytes in vitro and in vivo. Ligation of TIRC7 has important effects on the regulation of co-stimulatory signaling pathways associated with suppressing of T-cell activation. Targeting of TIRC7 may therefore provide a novel therapeutic approach for modulating T cell immune responses during organ transplantation. 相似文献
37.
Mana Taweevisit Putchong Isarakul Mookda Chaipipat Kanista Keetacheeva Vannee Wattanasirmkit Shanop Shuangshoti 《Neuropathology》2003,23(4):271-274
Cytokeratin (CK)7 and CK20, the low molecular weight cytokeratins, have been found to have a benefit in the differential diagnosis of some epithelial neoplasms. In the present study, the actual role of these markers in the search of primary tumors in 32 patients with craniospinal metastasis of an unknown primary site at presentation, is evaluated. A series of 36 patients with a known primary tumor were presented for comparison. In the first group, two CK7 and CK20 expression profiles were observed; 87% of metastatic tumors were CK7+/CK20‐ and 13% CK7‐/CK20‐. The lung was the major source (82%) of CK7+/CK20‐ metastatic tumors, whereas it represented only 38% of primary tumor in the second group of a known primary site (P = 0.006). Given the fact that metastatic tumors to the craniospinal axis of an unknown primary site are frequently CK7+/CK20‐, and they have commonly metastasized from the lung, it is doubtful that immunohistochemistry is really helpful. However, CT scan and MRI of the chest still play an important role. Many patients in the present study had to undertake these imaging studies, regardless of the CK7/CK20 result. The immunostains may be useful in cases with other expression profiles, but such examples constituted only a minority in the present study. 相似文献
38.
T. D. Sotnikova R. R. Gainetdinov T. V. Grekhova K. S. Raevskii 《Bulletin of experimental biology and medicine》1996,121(4):392-396
By means of intracerebral microdialysis it is shown that a selective agonist of the dopamine D3 receptors, 7-hydroxy-N,N-di-n-propyl-2-aminotetralin, causes a dose-dependent decrease of dopamine release but not its synthesis,
which confirms the preeminent involvement of D3 dopamine autoreceptors in presynaptic regulation of the release of this transmitter in the basal ganglia of rat brain.
Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 121, No. 4, pp. 430–434, April, 1996 相似文献
39.
Enhanced stimulus-reward learning by intra-amygdala administration of a D3 dopamine receptor agonist
The amygdala is considered to be a critical neural substrate underlying the formation of stimulus-reward associations, and
is known to receive substantial innervation from dopaminergic neurons located within the ventral mesencephalon. However, relat-
ively little is known about the function of the mesoamygdaloid dopamine projection in stimulus-reward learning. Recently,
we have found post-session intra-amygdala microinjections of d-amphetamine to enhance appetitive Pavlovian conditioning as assessed in a discriminative approach task. In the present study,
we have examined the effects of dopamine receptor agonists possessing relative selectivity for the D1, D2 and D3 receptor subtypes in order to examine more fully the role of the mesoamygdaloid dopamine projection in stimulus-reward learning.
Thus, subjects were trained to associate an initially neutral stimulus (CS+) with 10% sucrose reward (US). A second, control stimulus (CS−) was also presented but never paired with sucrose reward. In order to measure specifically the conditioned response to CS+/CS− presentation, responding during CS and US presentations was measured separately. Immediately following each training session,
subjects received bilateral intra-amygdala infusion of 0.1, 1 or 10 nmol/side of SKF-38393, quinpirole or 7-OH-DPAT. Infusions
of SKF-38393 or quinpirole were without effect on CS+ approach. However, post-session intra-amygdala infusions of 7-OH-DPAT enhanced selectively CS+ approach in a dose-dependent fashion. No dose of any drug affected CS−approach, US behaviours, or measures of extraneous behaviour. Subsequent acquisition of a novel conditioned instrumental response
was also unaffected. Thus, the present data indicate a selective involvement of the D3 dopamine receptor subtype in the modulation of stimulus-reward learning by the mesoamygdaloid dopamine projection.
Received: 12 December 1996 / Final version: 9 April 1997 相似文献
40.
用高效液相色谱跟踪2-甲基-7-亚甲基-1,4,6-三氧螺[4,4]壬烷(MMTN)与丙烯腈(AN),丙烯酸甲酯(MA)的共聚合反应。根据Lowry-Meyer共聚积分方程式,采用插值法进行数据拟合测定单体的竞聚率。对于体系MMTN(M_1)-AN(M_2),r_1=0.048;r_2=0.213;MMTN(M_1)-MA(M_2)r_1=0.025,r_2=0.764。说明两组共聚体系均有较强的交替共聚趋势。 相似文献